Stana Katic poses with her award at the 2014 People's Choice Awards in Los Angeles
IN PHOTO: Stana Katic poses with the award she won for favorite dramatic TV actress for her role in the series "Castle" at the 2014 People's Choice Awards in Los Angeles, California January 8, 2014. REUTERS Reuters/Kevork Djansezian

"Castle" Season 6, Episode 18, titled "The Way of the Ninja" airs this Monday, Mar. 17 on ABC. Kate Beckett (Stana Katic) and Rick Castle (Nathan Fillion) deal with the murder of a geisha with possible links to at least one suspected ninja assassin. Arden Cho ("Teen Wolf") is among the guest stars this week.

Spoiler alert: This feature contains spoilers on Castle Season 6 (and previous episodes). Read at your own risk. Episode 18, "The Way of the Ninja" follows "In the Belly of the Beast," which was aired on Mar. 3.

Stana Katic gave Casket shippers a shout out on Twitter over the weekend to show her gratitude for "an incredible 6-season" journey. See her tweet here. Meanwhile, ABC has not yet announced a Season 7. TVLine.com, however, believes Castle Season 7 is "a sure thing."

Watch a preview video of Castle Season 6, Episode 18 here. Rick Castle finds the possible murder weapon. But a ninja quickly steals the weapon from his hand. Then the said ninja just disappears into the mist. How will he convince Kate Beckett he is not making things up?

Watch Castle, Ryan (Seamus Dever) and Esposito (Jon Huertas) step into a geisha club. (Follow this link.) Viewers will feel right away the guys are inviting trouble in. Castle Season 6, Episode 18 does not seem to be one of the big episodes this year. Still, fans should watch to see the boys bond in their crime-solving schemes.

What lies ahead in the last half-dozen episodes of Castle Season 6? Senator William Bracken (Jack Coleman) is likely to resurface. Jerry Tyson aka 3XK (Michael Mosley) could also "rise from the dead." It may have been foreshadowed in an earlier episode this season.

Considering the big villains that could show up from late March to late May, many Caskett shippers are worrying over the wedding-that-should-happen. Some fans are even asking why Beckett is not wearing her engagement ring often enough.

"(Her engagement ring) is something that Beckett's very protective of, because she loves it," Stana Katic herself cleared things up on the engagement ring worries. Apparently, Beckett wants to keep things "professional" in Castle Season 6. After all, wearing a lovely rock at the workplace is simply "not appropriate" for a detective, Katic told TVLine.com.

The Castle Season 6 finale is hoped to feature the Caskett wedding. There are still six episodes before the finale, so it could still happen before the show takes its summer break.

More TV Guide and Spoiler Features

'Castle' Season 6 Spoilers: Stana Katic Shares BTS Photos; Rick Cheats On Beckett? Watch 'Ninja' After the 'Beast' [Promo Video]
'Castle' Season 6, Episode 17 Spoilers: Stana Katic Talks Wedding Plans and 'Belly of the Beast' Thrill [Watch Promo Video]
'Once Upon A Time' Season 3 Spoilers: Wicked Witch vs Evil Queen, Emma Swan and Snow White [Watch Promo Video]